"He was a war hero, safe overseas miraculously, comes back here and dies in the line of duty," Hansen said.

Hansen has participated in the Police Unity Tour seven times in the past eight years in honor of Birkholz, his lifelong friend and his daughter's godfather.

The national tour began in 1997 to raise awareness of officers killed on duty and raise money for the national memorial.

Hansen and 53 other cyclists from Wisconsin, including officers and survivors of fallen officers, flew to Philadelphia and biked to Washington, D.C., over four days, arriving at the memorial on Sunday.

“You can’t explain what it means until you experience it," Hansen said. "They are people who understand exactly what you’ve gone through and you don’t have to explain. You’re among people who get it.”

Hansen did not do any cycling before joining the Police Unity Tour. He met a group of tour riders who participated in a separate cycling event to raise money for a fund in Birkholz's name. He liked the idea of honoring his friend and other fallen officers in that way.

"Anytime it gets difficult, we look down and you see the bracelet and remind ourselves of the sacrifice they made," he said. "The least we can do is pedal on."

On Monday, Hansen and a few other tour riders walked through the memorial, making a point to pause at Birkholz's name, one of nearly 22,000 etched in stone.

“These heroes cannot be forgotten," he said. “There are so many great stories behind every name on this wall.”